All I can do is speak from my own experience. I can't say that anyone else is right or wrong from their own experiences.
ATK saved my battery on my new DX. Plain and simple. It was running all sorts of applications that it didn't need to be like Amazon MP3, Maps, Music and several others. I had ATK on my Moto Droid, but didn't want to install it on the DX until I saw how it was running. Plain and simple - all the running apps were draining the crap out of the battery.
I installed ATK onto my DX and have had zero issues. It's preserved a better battery life for me and I have zero issues running the task killer. I select which apps I want it to ignore, and when I close it it kills what I want it to. Even checking just now, Music is running along with Amazon MP3. Why? I dunno. I haven't used either of them since getting the phone on launch day.
I also work in IT as a network Administrator, and even your operating system comes with a Task Manager that allows you to kill the applications you want. My feeling is that with your smart phone, you should have the same thing.
It's a free app. In the end, if you try it and it doesn't work for you - then you've lost nothing. But if it does work for you, then you're better for it.
Just my 2 cents, nothing more.
How was it draining the crap outa your battery? Idle apps use extremely little memory and dont use the cpu. You're draining more battery opening up your task killer and closing the apps that Android itself is most likely going to reopen in the background anyway
The ATK runs in the background itself. I do nothing after the set up. When I close my phone, any applications that I don't have selected as "Ignore" are then shut down.
On launch day, like everyone else, I played with the phone - a lot. Found the battery dying rather quickly. No worries - will charge the battery over night.
Friday morning, took it off of the charger and took it to work. Didn't play with it much, showed it off a wee bit and by the time I got home after a 9 hour day, the battery was nearly dead. Now mind you, I was not leaving anything running. I "let the OS do it's thing". Wondering why it was dying so quickly, I looked at all the open applications....things I didn't even open were running - Maps, Navigation, Amazon, Radio...essentially a list of what's what on the phone.
Saturday, didn't use it much and after a full night charge, it was below 50% usage.
Sunday I installed ATK on the DX. Now, in all fairness I had it on the Moto Droid and it helped. I didn't install it right away because I wanted to see how the phone battery was, and I had read several reviews how the phone battery was lasting a long time. I was a tad disappointed.
Now since the recent update today, I'm very tempted to take off ATK and see how it runs without it. I'm hoping I don't need it.
But like I mentioned before - All I can go by is my own experience and what has worked and not worked for me. I'm not saying what anyone else is suggesting is right or wrong by any means. Just strictly going by my own experience.